Continuous and discontinuous gradients are used to separate a wide variety of components including cells and subcellular components. Several gradient makers are commercially available. These gradient formers lack the versatility to deliver both multiple identical continuous and discontinuous gradients. None of the gradient makers presently available is able to make multiple gradients of analytical quality. These gradient makers are often difficult to regulate and require time consuming manipulations.
Gradients are usually generated by devices which have two chambers. One of the chambers serves as the mixing chamber, and from this reservoir one or more delivery lines and a pump are used to transfer the gradients to their receivers. This method permits one to form several gradients, but, unfortunately, the gradients are often of unequal volume and/or unequal gradient shape. These defects occur when the flow rates of the gradient material in the delivery lines are unequal due to small differences in the diameters of the tubing.
A number of devices have been disclosed for providing samples of different dilutions, although most of these devices are rather complex. Buckley, in U.S. Pat. No. 3,525,592, discloses a liquid sampling device for continuously taking measured samples of blood and diluting them with measured quantities of liquid. The apparatus comprises a probe, a first syringe, the cylinder of which is connected to the probe by a closed conduit, a second syringe, the cylinder of which is connected by a second closed conduit to a liquid diluent container, a third closed conduit connecting the second conduit to the first conduit, a two-way valve between the second and third conduits, and means for actuating the syringes and valves so that the first syringe draws a measured volume of sample into the probe and ejects it therefrom, and the second syringe ejects a measured volume of diluent from the container through the probe behind the ejected sample.
Feichtmeir et al., in U.S. Pat. No. 3,127,062, discloses a semiautomatic sampling and diluting apparatus comprising a first powered precision displacement volumetric chamber for measuring and delivering a fluid from the chamber, and a second similar chamber for measuring and delivering a second fluid in admixture with the first. A precision ground plunger is provided in the volumetric chambers. Feichtmeier, in U.S. Pat. No. 3,102,863, discloses a calibrated pipette which forms a means into which a predetermined volume of fluid sample may be drawn, and a variable volume chamber means which may be calibrated to contain a predetermined volume of diluent or reagent. Control valve means are provided which in a first position simultaneously connect the chamber with a storage reservoir source so that the predetermined volume of diluent may be introduced into the chamber and the desired volume of sample may be drawn into the pipette.
Sequeira, in U.S. Pat. No. 3,327,535, discloses a multiple pipette apparatus including a line of pipetting tubes mounted on a member extending along a support, the tubes individually communicating through pipes with piston-and-cylinder units operated in synchronism to draw liquid simultaneously from the pipetting tubes.
These prior devices do not provide serial dilutions of continuous and discontinuous gradients, and using varying ratios of batteries of syringes generating vacuum to syringes delivering gradient material.